Abstract

Volcanic ash falls are one of the most widespread and frequent volcanic hazards, and are produced by all explosive volcanic eruptions. Ash falls are arguably the most disruptive volcanic hazard because of their ability to affect large areas and to impact a wide range of assets, even at relatively small thicknesses. From an insurance perspective, the most valuable insured assets are buildings. Ash fall vulnerability curves or functions, which relate the magnitude of ash fall to likely damage, are the most developed for buildings, although there have been important recent advances for agriculture and infrastructure. In this paper, we focus on existing vulnerability functions developed for volcanic ash fall impact on buildings, and apply them to a hypothetical building portfolio impacted by a modern-day Tambora 1815 eruption scenario. We compare and contrast the different developed functions and discuss some of the issues surrounding estimation of potential building damage following a volcanic eruption. We found substantial variability in the different vulnerability estimates, which contribute to large uncertainties when estimating potential building damage and loss. Given the lack of detailed and published studies of building damage resulting from ash fall this is not surprising, although it also appears to be the case for other natural hazards for which there are far more empirical damage data. Notwithstanding the potential limitations of some empirical data in constraining vulnerability functions, efforts are required to improve our estimates of building damage under ash fall loading through the collection of damage data, experimental testing and perhaps theoretical failure analysis. For insurance purposes, the current building typologies provided for use with vulnerability functions are too detailed to map to the relatively limited information on building types that is typically available to insurers. Thus, efforts to provide vulnerability functions that can be used where only limited information is available regarding building types would also be valuable, both for insurers and for at-risk areas that have not been subject to detailed building vulnerability surveys.

Highlights

  • This paper focuses on the vulnerability of buildings to tephra falls, summarising recent efforts to compare the existing approaches and estimates, and investigating how differing approaches could affect damage estimates

  • In this paper, we compare and contrast existing vulnerability functions that have been developed for volcanic ash fall on buildings, and apply them to a hypothetical building portfolio impacted by a modern-day Tambora 1815 eruption scenario

  • We found there is considerable variability in the different vulnerability estimates even for reasonably tightly specified construction types, which contributed to large uncertainties when estimating potential building damage and loss

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Summary

Introduction

This paper focuses on the vulnerability of buildings to tephra falls, summarising recent efforts to compare the existing approaches and estimates, and investigating how differing approaches could affect damage estimates. Ash fall vulnerability estimates are more developed for buildings as the mechanism through which damage occurs is typically distinct (loading), whereas for pyroclastic density currents, for example, hazard parameters include temperature and lateral pressure, as well as the duration of these impact mechanisms on the structure (Blong 2003; Spence et al 2005; Jenkins et al 2014). Ash fall vulnerability and fragility functions ( known as curves) developed for specific building types link the local intensity of ash fall (thickness or loading) to probable levels of damage, often with levels of uncertainty described. Our aim is to highlight the sensitivity of loss and damage calculations to functions that describe the vulnerability of an asset to a volcanic hazard. We concentrate on building response to volcanic ash fall

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